There currently exists a numerous types of electronic integrated circuits (IC's) for use in the automotive industry. Generally, the power supply for these circuits are generated from a 12-volt battery in an automobile. However, automotive IC's tied to the battery must survive the battery being hooked up backwards, for example, to avoid forward biasing epitaxial layers of the IC that are tied to the battery which thereby could result in destruction of the IC.
One attempt that prior art has made for providing reverse battery protection for IC's is to include a series diode between the battery and the integrated circuit wherein if the integrated circuit is connected to the battery backwards, the series diode is reversed biased and prevents supply voltage from being applied to the integrated circuit. However, the series diode solution compromises low voltage performance and the geometry of the diode becomes larger as supply current requirements increase.
Another attempt that prior art has made in providing reverse battery protection for an integrated circuit is to provide a saturated lateral PNP transistor in series between the battery and the integrated circuit. Although low voltage performance is not compromised in this solution, base current requirements for the lateral PNP increase power dissipation and the geometry of the PNP transistor becomes large as supply current requirements increase.
Another attempt that prior art has made in providing reverse battery protection for an integrated circuit is to provide a charged pumped reverse TMOS transistor as a pass device between the battery and the integrated circuit wherein the TMOS transistor has passive (resistive) gate to source termination. However, this solution requires DC current from the charge pump to enhance the TMOS transistor, and the turn off time of the TMOS transistor is limited by the size of the passive gate termination. Moreover, the charge pump must be high impedance when the supply voltage is reversed.
Hence, there exists a need for an improved reverse battery protection circuit for an integrated circuit that does not compromise low voltage performance, can efficiently handle moderate supply currents, does not demand DC current from a charge pump, and has a fast turn off time.